Early success in the treatment of congenital pseudoarthrosis of the tibia in children and of disuse osteoporosis in animals using an electromagnetic field suggests that the proper manipulation of bioelectric phenomena might prove efficacious in patients with osteogenesis imperfecta and in patients with idiopathic or senile osteoporosis. This study has been designed to test this hypothesis, concentrating initially on the effect of an electromagnetic field on disuse osteoporosis in animals in order to resolve unanswered questions regarding desirable vs. undesirable pulse characteristics, and to gain better insight into the effect of such treatment on epiphyseal growth. In vivo studies will include an evaluation of cortical bond using X-rays and of trabecular bone using computerized axial tomography; in addition, stress wave propagation through the intact bone will be measured using a previously designed noninvasive electromagnetic device as an index of the material properties of the bone. In vitro studies will include measurements of the physical properties of both cortical and trabecular bone, and microscopic evaluation of the cellular response in bone.